Super Tuesday: Polarisation of US politics likely to gather pace

Voters predicted to ditch Congress moderates in favour of strident candidates from extremes of right and left

Barack Obama walks back after delivering a statement on the budget that he sent to Congress earlier this year. The increased polarisation of US politics is likely to weaken the president's position. Photograph: Pablo Martinez Monsivais/AP

The polarisation of US politics is likely to gather pace tomorrow in a host of contests across the country in which Republican and Democratic establishment candidates face being thrown out, victims of a wave of populist hostility towards Washington.

The contests, labelled Super Tuesday 2010, amount to the biggest test of the US public mood since Barack Obama was elected two years ago.

The elections, mainly primaries to choose candidates to stand in the congressional midterm elections in November, are being held in Pennsylvania, Kentucky, Arkansas and Oregon.

"We are seeing a lot of longterm entrenched incumbents up for re-election and people deciding to send them packing," said Brad Coker, head of the DC-based Mason-Dixon polling and research company.

Coker said he had witnessed anti-incumbent moods against one party in almost three decades of covering politics but never both at the same time. "It is out with the old and in with the new," he said. "Experience in Washington is not the first thing voters are looking for: in fact it is probably bottom of the list."

Politicians in both parties are reporting a recession-driven sourness among the electorate. Republicans backed by the party establishment are facing challenges from candidates supported by Tea Party activists, the anti-big spending movement that began last year and is pushing the party to the right.

Democratic candidates supported by the White House are also in trouble, facing strong challenges from candidates from the left.

All 435 seats in the House of Representatives will be contested in November along with 36 of the 100 Senate seats. There is little bipartisan co-operation in Congress now and there is likely to be even less next year if rightwing Republicans and leftwing Democrats prevail tomorrow.

The Tea Party activists, emboldened by big recent victories in Utah and Florida, are pinning their hopes on Rand Paul, a doctor who seeks the Republican nomination for a congressional seat in Kentucky.

Paul, son of congressman Ron Paul, one of the biggest champions in the US of small government, has been consistently leading in the polls over Trey Grayson, who is the choice of the Republican establishment in Washington.

Obama's position will probably be less strong after the November congressional elections because the Democrats are almost certain to have fewer seats in both the Senate and the House of Representatives.